Floating roof for resisting air or gas shock waves



FLOATING ROOF FOR RESISTING AIR OR GAS SHOCK WAVES Filed Aug. 29, 1955June 10, 1958 J H. WIGGINS 2 Sheets-Sheet 1 3 N QK INVENTOR. JOHN H.W/GG/NS 7 ATTORNEY June 10, 1958 J. H. WIGGINS 2,838,199

FLOATING ROOF FOR RESISTING AIR OR GAS SHOCK WAVES Filed Aug. 29, 1955 2Sheets-Sheet 2 MHHHHH INVEN TOR. JOHN h. W/GG/NS 2 ATTORNEY 2,838,199Patented June 10, 1958 Free , v A 7 2,838,199 FLOATING ROOF FORRESISTING AIR 01: GAS

V SHOCK WAVES A from H. Wiggins, Woodside, Calif. Application Augus't29,1955, Serial No. 53l,082

8 Claims. (Cl. 220-2 The present invention relatesto floating roofs forliquid storage tanks of the type commonly employed in the oil industryfor storing various types of petroleum products, and is concerned moreparticularly with a pontoon ,type floating roof which is constructed toresist air or gas shock waves of the type caused by internal explosionswithin one of the pontoons, or of the type caused by a' nearby atomicexplosion.

Pontoon type floating roofs are subject to internal explosions whenevera. leak occurs in the bottom deck, and an explosive mixture 'is gatheredwithin the pontoon, and subjected to a'spark or flame. An explosionwithin a pontoon can g'enerateint'ernal pressures as high as 45 lbs. tothe square inch. Also it is known that an atomic explosion is followedby a positive pressure wave with pressures in the neighborhood of 12 lbsper square inch,

and a subsequent negative or reduced pressure wave with nega 'vepressures of approximately lbs. per square inch. i

The building of a pontoon roof of a strength to withstand internalexplosions is such an expensive'project as to be entirely impractical,and I have solved this problem by providing a roof structure whichserves to relieve internal explosions by venting and to-withstandexternal pressures structurally.

Accordingly it is a general object of the invention to design apractical, relatively inexpensive roof which is adapted to relievepressure Withi'n'the roof in case of an explosion in a closed pontoon,and to withstand external air shock waves. W I I Another objectof theinvention is to provide a floating roof of the pontoon type of anautomatic self-Venting nature as to pass through an explosive or anatomic shock wave inv undamaged condition.

Another object of the invention is to provide a floating roofstructurein accordance with the foregoing ob- 'ects, and one which canalso be easily adapted to the reconstruction of. existing floatingroofs.

The above and other objects of the invention are attainedas described inconnection with a' preferred embodiment'of the invention, as illustratedin the attached drawings, in which:

Fig. .1 is a transverse sectional'view through one half of.a'fstoragetank incorporating a pontoon type floating roof, constructedin accordance with the instant invention, the 'planeof the view beingindicated by the line 1-4 in Fig. 3. H A

Fig. 2 ,is afragmentary sectional view taken in a plane indicated by theline 22 in Fig. 3.

Fig. 3 is a fragmentary plan view with certain parts brokenaway toillustrate certain details of construction.

The roof structureof the instant invention is incorporated in afloating'roof of the type described in my U. S. Letters Patent2,430,592, dated November 11, 1947, to which reference is made forfeatures not shown or described in detail herein. Referring to thedrawings, there is shown an oil storage tank including a side wall 10anda bottom Wall 12, the sidewall 10 being shown 2 as a conventionalmetal section, which maybe reinforced and protected by an earthenembankment not shown. The liquid 13 in the tank has a floating roof 14thereon. The floating roof 14 includes a bottom deck 15 of suitablesheet metal plate structure, which slants outwardly and downwardly froma central portion 16, where a center post 17 is secured thereon inupright position, to a low point 18 which is immediately adjacent theouter rim or wall 19 of the center pontoon 21.. The low region 18 formsan annular drainage area. From the low point 18 deck 15 slopes upwardlyto its outer edge which'is joined to the annular outer pontoon 22approximately midway of the height of an inner wall 23 thereof. Thepontoon 22 also includes a bottom wall 24, a top wall 26, and anouterwall 27.

v The outer pontoon 22 is preferably a compartmented construction, andis separated into compartments by series of bulkheads 28, eachcompartment havingan upwardly directed'jmanhole or vent openings formedby a pipe 29 which is closed by a ventcap or manhole cover 31. Eachcover 31 is secured frictionally in place, so as to be easily displacedwhen a low internal pressure is generated to vent this pressure toatmosphere. The size of the compartments, and the construction of thewalls of the outer pontoon 22 are such that the compartments willwithstand external pressures Within the ranges noted, and will standinternal pressure until the rise in pressure removes the cover 31 andthe pressure is thereby vented to atmosphere. a Y z The center pontoon21, in addition to the. outer rim 19 includes a series of radiallyextending truss structures 32.which extend between the center post 17,and the] outer rim orwall 19 and'are generally conventional constop uponupward movement of the roof.

struction including in general conventional structural elements. Ifdesired the truss structures 32 may be replaced by suitable bulkheads. I

The roof 33 of the center pontoon is This ro'ot'33 is composed offlexible sheet metal plate structure and the center of the roof 33 isapertured at 34 to engage about the center post 17, this center post 17is provided with a top 'flange'17a which operates as a At various pointsaround the roof, it is 'suppliedwith upwardly directed vent openings,each including" an upstanding pipe 36, having a manhole cover 37frictionally secured therein, so as to be displaced easily therefrom.

A The top deck or roof 33 of the pontoon structure is constructed juststeep enough so that the roof will drain properly and shallow enough sothat the peripheral edge of the roof may flex up several feet, theamountdepending on the diameter of the pontoon, and this roof is provided witha depending flange 33:: which overlaps the outer rim 19 of the pontoon,to insure proper shedding of the water.

Intermediate the truss structures 32, the center pontoon 21 is providedwith a plurality of spaced upright posts or shock resisting members 38,which are shown in the drawing as cylinders, although any suitablestructural member may be employed. These cylinders 38 are secured to thebottom deck 15, and have their tops disposed to form a continuation ofthe surface defined bythe truss structures 32 and the outer rim 19. Whena shock wave is encountered such as caused by an internal explosion, theentire roof or top deck of the center pontoon rises until its centerengages and is stopped by the flange 17a of the center post 17. Then ifthe pressure is suflicient the roof will continue to flex upwardly witha reverse slope until it reaches approximately the phantom line positionshown in Fig. 1. During this of flexible con-f V struction-,pand 1sconnected to the pontoon in "a novel' upward flexing the dependingflange 33a acts as a compression member to resist collapse of the edge.the fact that the roof moving as a whole engages the flange 17a as astop, and thereafter flexes, the flexing of the roof acts as a shockabsorber which prevents the roof from being damaged.

With a pitch of the roof of from about in 12" of radius to about 1" in12" of radius, the roof can flex up and wrinkle and flex down andwrinkle again without any damage thereto. On a 120' diameter tank, thecenter pontoon would be approximately 30' in radius, and the desirablerise of the roof to the flange 17a would be about 18". rise about 30 toa horizontal plane, and about 25" more to its maximum reversed slopebefore the peripheral flange 33a would be put into compression by thetension in the roof plates. This would give a total peripheral rise ofabout 73", and the venting area would be about 1140 square feet to venta volume of about 20,000 cubic feet of gases. With this relation ofparts the velocity required to vent the pontoon in one second is lessthan 20 ft. per second which would require a very low pressure to eflectcomplete venting.

From the above description it will be seen that I have provided afloating roof structure of the pontoon type, which is automaticallyvented in the case of severe internal rises in pressure, and whichoperates automatically to relieve such pressure and to return to itsnormal condition. This roof can be constructed at a cost substantiallyequal to the conventional type pontoon roof.

While I have shown and described a preferred embodiment of theinvention, it is apparent that the invention is capable of variation andmodification from the form shown, so that the scope thereof should belimited only by the proper scope of the claims appended hereto.

I claim:

1. An explosion and shockproof floating roof for tanks of the oilstorage type comprising a deck for floating engagement throughoutsubstantially its entire area with the liquid in the tank, and a centerpontoon structure including an upstanding center guide post secured tosaid deck, an upstanding outer Wall secured to said deck, a plurality ofupwardly extending frame and support elements secured to said deck anddisposed between said post and said wall, a flexible, sheet-metal rooffor said center pontoon structure having sliding engagement with saidpost and normally resting freely upon the tops of said wall and saidsupport elements, said wall and said support elements having relativeheights such that said flexible roof is supported thereby in awater-shedding configuration and is supported thereby so as to withstandexternal pressures that may be applied to the upper surface of saidflexible roof, said roof being adapted to be lifted bodily about saidguide post and upwardly out of contact with said wall and said supportelements upon occurrence of an explosion within said center pontoon,thereby venting the interior of said center pontoon, and a stop on saidpost for limiting upward movement of said roof, said roof having byvirtue of its flexibility a freely liftable outer periphery which flexesupwardly with respect to the center portion of Due to t The periphery ofthe roof could 1 said roof in response to the internal pressure createdby said explosion within said center pontoon, thereby increasing thespeed with which said internal pressure is relieved from the interior ofsaid center pontoon.

2. An explosion and shockproof floating roof for tanks of the oilstorage type comprising a deck for floating engagement throughoutsubstantially its entire area with the liquid in the tank, an outerpontoon structure secured to the outer edge of said deck including aseries of compartments each having an upwardly directed opening, eachopening being provided with a cover that is readily removed by pressurefrom within the compartment, and a center pontoon structure including anupstanding center guide post secured to said deck, an upstanding outerwall secured to said deck, a plurality of upwardly extending frame andsupport elements secured to said deck and disposed between said post andsaid wall, a flexible, sheetmetal roof for said center pontoon structurehaving sliding engagement with said post and normally resting freelyupon the tops of said wall and said support elements, said wall and saidsupport elements having relative heights such that said flexible roof issupported thereby in a water-shedding configuration and is supportedthereby so as to withstand external pressures that may be applied to theupper surface of said flexible roof, said roof being adapted to belifted bodily about said guide post and upwardly out of contact withsaid wall and said support elements upon occurrence of an explosionwithin said center pontoon, thereby venting the interior or said centerpontoon, and a stop on said post for limiting upward movement of saidroof, said roof having by virtue of its flexibility a freely liftableouter periphery which flexes upwardly with respect to the center portionof said roof in response to the internal pressure created by saidexplosion within said center pontoon, thereby increasing the speed withwhich said internal pressure is relieved from the interior of saidcenter pontoon.

3. In an explosion and shock-proof floating roof for oil storage tanksand the like, a deck for floating engagement with liquid contained insuch tank, and a center pontoon structure including an upstanding centerguide post secured to said deck, an upstanding outer wall also securedto said deck in spaced relation with said guide post, support elementssecured to said deck and disposed intermediate said guide post and saidwall, a flexible roof for said pontoon structure normally resting uponthe tops of said wall and said support elements, said roof having acentral opening therein passing said guide post therethrough and beinglongitudinally movable with respect thereto, said roof being adapted tobe lifted bodily along said guide post and upwardly from said wall andsaid support elements upon occurrence of an explosion withn said centerpontoon, thereby venting the interior thereof, and a stop carried bysaid guide post for limiting upward movement of said roof, said roofhaving by virtue of its flexibility a freely liftable outer portionwhich flexes upwardly with respect to the center portion thereof 3::response to internal pressure increases created by an explosion withinsaid center pontoon, thereby increasing the speed with which suchinternal pressure is relieved from the interior of said center pontoon.

4. The structure of claim 3 in which said roof is equipped with adepending perimetric rim adjacent the outer edge thereof adapted tofunction as a compression member upon upward flexing of said roof.

5. In an explosion and shock-proof floating roof adapted for use in oilstorage tanks, a deck for floating engage ment with liquid contained insuch tank, and a center pontoon structure disposed well inwardly of theouter boundary of said deck and comprising a perimetric wall secured tosaid deck and extending upwardly therefrom, a flexible roof having anouter edge portion carried by said wall and extending inwardlytherefrom, support means provided by said deck inwardly of said wall forreceiving said roof to support the same in spaced, covering relationwith respect to said deck, guide means carried by said deck andcooperating with said roof for mounting said root for bodily upwardmovement relative to said deck, and means for limiting such upwardmovement of said roof with respect to said deck, said roof being adaptedto be lifted bodily upwardly and out of contact with said wall uponoccurrence of an explosion within said center pontoon and, by virtue ofits flexibility, having an upwardly deflectible outer portion whichflexes upwardly with respect to the center portion thereof in responseto an increase in pressure within said center pontoon created by anexplosion therein, thereby incr a $ing e speed with which such pressureequipped with a depending perimetric rim adjacent the outer edge thereofadapted to function as a compression member upon upward flexing of saidroof.

7. The structure of claim 5 in which said center pontoon iscompartmented, in which said roof is provided with a plurality ofopenings therein respectively communicating with at least certain ofsaid compartments, and in which each of said openings is equipped with acover removable therefrom by explosion-created pressure increasesoccurring within said center pontoon.

8. An explosion and shock proo-f floating roof adapted for :use with oilstorage tanks, comprising a deck for floating engagement throughoutsubstantially its entire area with liquid contained within such tank, anouter pontoon structure secured to said deck'and including a pluralityof compartments each having an upwardly directed opening therein, eachof said openings being provided with a cover removable therefrombyexplosioncreated pressure increases occurring within said outer pontoon,and a center pontoon structure including an upstanding center guide postsecured to said deck, an upstanding outer wall also secured to said deckin spaced relation with said guide post, support elements secured tosaid deck and disposed intermediate said guide post and said wall, aflexible roof for said pontoon structure I normally resting. upon thetops of said wall and said support elements, said roof having a centralopening therein passing said guide post therethrough and beinglongitudinally movable with respect thereto, said-roof being adapted tobe lifted bodily along said guide post and upwardly from said wall andsaid support elements upon occurrence of an explosion within said centerpontoon, thereby venting the interior thereof, and a stopkarried by saidguide post for limiting upward movement of said roof, said roof havingby virtue of its flexibility a freely liftable outer portion whichflexes upwardly with-respect to the center portion thereof in responseto internal pressure increases created by an explosion within saidcenter pontoon, thereby increasing the speed with which such internalpressure is relieved from the interior of said center pontoon. V VReferences Cited in the file of this patent UNITED STATES PATENTS SmithMay 6, 1913 1,287,223 Ca'they Dec. 10, 1918 1,343,480 Rutherford June15, 1920 2,302,904 Wiggins Nov. 24, 1942 2,430,592 Wiggins Nov. 11,'1947 2,605,014 Wiggins et a1. July 29, 1952 2,616,586 Lamb Nov. 4, 1952

